Exemplary embodiments of the present invention relate to a seat belt for a vehicle, comprising a belt webbing that comprises several belt webbing layers and, in a shoulder belt region and a lap belt region, at least one belt interior which is located between at least two belt webbing layers and to which a gas can be applied, wherein the belt webbing is guided through an opening of a latch plate which can be inserted into a buckle, by means of which latch plate the belt webbing is, if the seat belt is fastened, deflected at a lower deflection point in a transitional region from the lap belt region to the shoulder belt region, and wherein a gas passage connecting at least two sections of the belt interior is provided at the lower deflection point between the at least two belt webbing layers.
German Patent Document DE 91 03 845 U1 discloses a restraint device for occupants of a vehicle. The restraint device comprises a seat belt with a buckle and a deflection fitting. The seat belt is designed as a flat tube and coupled to a device by means of which the tube, in an accident-related sudden deceleration of the vehicle equipped therewith, can be inflated within fractions of a second with a gas, turning it into a tube with a substantially circular cross-section.
German Patent Document DE 198 57 517 A1 disclose an inflatable belt webbing for a seat belt made of a two-layered woven fabric. A webbing width of the fabric is divided into three parts of approximately equal width, these being a left-hand outer part, a central part and a right-hand outer part, the warp threads of the parts differing in thickness. The outer parts and the inner part are folded in such a way that they form a flattened Z. In two folding zones, at least one tear-open thread is woven or sewn into the fabric, the tear-open thread breaking under a presettable breaking load, so that the individual fabric layers move in preset directions and the belt webbing is opened by means of a blown-in explosion gas to form an inflated belt bag. In order to apply gas to the belt webbing, a gas delivery hose is provided, is placed in the belt webbing between darts. For inflation, the belt webbing is supplied with the explosion gas by means of the gas delivery hose.
European Patent Document EP 1 053 133 B1 describes a three-point belt with shoulder and lap belt parts of a belt webbing, which are inflatable at least in the shoulder belt region. At a deflection point, the seat belt is provided with an insertion part that can be inserted into a buckle, the belt webbing being deflected in a transitional region from the lap belt part to the shoulder belt part at the deflection point if the seat belt is fastened. In the region of the insertion part, the belt webbing is provided at the deflection point with a gas passage for establishing a gas flow connection between the belt interiors of the shoulder belt part and the lap belt part. An opening cross-section of the gas passage is smaller than the cross-section of a filled belt interior, which can be filled continuously and extends in the belt webbing that forms the shoulder and lap belt parts as well as in the transitional region. At least in the belt interior of the transitional region guided around the deflection point, the gas passage forms a radially reinforced gas line via the opening cross-section of which the interiors of the shoulder belt part and the lap belt part can be inflated. The gas passage consists of a tubular piece having a relatively high rigidity in the radial direction, so that the opening cross-section formed by the gas passage does not collapse as the belt webbing is deflected about the deflection point. The seat belt further comprises a gas feed in the region of an end of the lap belt part that is opposite the transitional region.
In a German Patent application number 10 2010 023 875.9, which is not subject to prior publication, a seat belt for a vehicle is described, which seat belt comprises an inflatable belt webbing. A gas passage consisting of a tube which is flexible at least in the radial direction extends in the belt webbing passing through an opening in the latch plate.
One disadvantage of these known inflatable seat belts is that during the inflation process high gas pressures act internally on the seat belt due to the high speed with which the belt webbing has to be inflated in an accident. In this process, the belt webbing is increasingly stressed, in particular if subjected to pulsed maximum pressure loads. In order to avoid any damage caused by this stressing of the belt webbing, which would affect its function, the belt webbing has to be designed to be correspondingly complex, for example by using a reinforced belt webbing fabric.
Exemplary embodiments of the present invention are directed to providing a seat belt for a vehicle that is improved compared to prior art.
In accordance with exemplary embodiments of the present invention, a seat belt for a vehicle comprises a belt webbing having several belt webbing layers and, in a shoulder belt region and a lap belt region, at least one belt interior that is located between at least two belt webbing layers and to which a gas can be applied, wherein the belt webbing is guided through a recess of a latch plate which can be inserted into a buckle, by means of which latch plate the belt webbing is, if the seat belt is fastened, deflected at a lower deflection point in a transitional region from the lap belt region to the shoulder belt region, and wherein a gas passage connecting at least two sections of the belt interior is provided at the lower deflection point between the at least two belt webbing layers.
The two sections of the belt interior are formed by the deflection of the belt webbing in the region of the latch plate and the resulting tensile and compressive forces.
The gas passage is represented by a tube which is flexible, i.e. collapsible, at least in the radial direction.
If gas is applied to the belt interiors in order to increase a surface area of the belt webbing, which happens if the vehicle collides with an obstacle, the tube forms an open flow cross-section due to the internal pressure acting in the interior of the tube. Accordingly, even the shoulder region of the seat belt can be filled with gas from a gas generator located at a lower mounting point of the belt webbing, even though the belt webbing is deflected at the lower deflection point. This results in an optimized gas filling of the belt webbing. The gas may be, for example, air or reaction gases generated in a pyrotechnic gas generator and by the ignition of the fuel charge.
According to the invention, the tube, which is designed to be flexible as a gas passage, is elastically deformable.
Due to this elasticity of the tube, a so-called Windkessel effect as known in medicine in relation to blood vessels located near the heart, such as the aorta, is obtained. As the belt webbing is filled with gas, the gas of the gas generator connected to one end of the tube first flows through the elastic tube before the gas flows from the open other end of the tube into the inflatable belt webbing. Due to its elasticity, the elastic tube expands in proportion to the gas pressure acting on the tube. If the pressure is reduced, the tube at least partially contracts in proportion to the pressure acting on the tube, thereby forming a type of pressure accumulator. In this way, gas pressure peaks are attenuated, so that the belt webbing is stressed less severely. If restricted at bends, kinks, hangers and guides, the belt can moreover locally expand radially to a degree sufficient to allow the pressure wave pass through the restriction in the tube. Tube sections located at a greater distance from the gas generator can be filled with an adequate gas pressure as well.
In an alternative embodiment, the tube, which is designed to be flexible as a gas passage, is plastically deformable. As pressure is reduced, the tube, unlike the elastic tube, cannot contract again and therefore does not act as a pressure accumulator. Pulsed pressure peaks can, however, be attenuated by the plastic expansion of the tube as well, and the use of a plastically deformable material may be simpler, for example cheaper.
In principle, the elastic tube can also be used to attenuate pulsed maximum pressure loads without connecting two sections of the belt interior. In this embodiment, one end of the tube is directly connected to the gas generator and the other end terminates in a belt interior of the inflatable belt webbing which is adjacent to the gas generator.
In a further development, the elasticity of the tube is at least so high that the internal cavity radius reversibly increases by 10% or more at a gas pressure peak relative to normal pressure, in order to obtain a significant Windkessel effect.
In a further embodiment, the tube has only a minimum elasticity along its longitudinal axis, so that the position of the end of the tube through which the belt webbing is filled with gas is not changed by longitudinal expansion. An elasticity perpendicular to the longitudinal axis does not cause any problems in this respect.
In a further development, the tube is compressed flat between the belt webbing layers if the belt webbing is not filled with gas. As a result of this design of the gas passage as a collapsible tube lying flat between the belt webbing layers, the belt webbing is flexible and can be retracted and paid out simply, using little force. The belt webbing can also be easily displaced within the latch plate. In addition, due to the flexible design of the tube and thus of the belt webbing, the belt webbing can be positioned optimally on the vehicle occupant, invariably offering maximum protection. The flexibility of the belt webbing and the simple retraction and pay-out of the belt webbing results, in addition to advantageous haptics, in a high level of comfort for the vehicle occupant.
The tube is further preferably designed to be seamless, improving its tightness against radially escaping gas. According to a further development of the invention, the tube is woven seamlessly using generally known methods. The fabric is preferably a synthetic fiber fabric, in particular a polyester yarn fabric, which is characterised by a particularly high stability. As the tube is made of a woven fabric, it can easily be inserted into the belt webbing in a flat state.
An inside of the tube is then preferably coated with a fluid-impermeable layer, in particular with latex or silicone. In this way, the tube is made fluid-tight. This ensures that the connection of the belt interior between the lap belt region and the shoulder belt region is not broken in the gas filling process, because a gas escape from the tube in the radial direction is avoided.
In order to avoid a slipping of the tube within the belt webbing while the seat belt is fastened and removed and in its fastened state, the tube is secured to at least one of the belt webbing layers in a further development. This is, for example, carried out by bonding the tube to the inside of the belt webbing layer in question. The resulting adhesive seam preferably has only a small width, allowing the tube to unfold optimally.
If the latch plate is inserted into the buckle and at a minimum pay-out length of the belt webbing, the tube preferably extends no further than an upper deflection point. This means that the tube, if the seat belt is fastened, extends no further than the upper deflection point, which is preferably located in the upper region next to the vehicle occupant or the vehicle seat. In addition, the inflatable belt interior extends no further than the upper deflection point in the shoulder belt region at a minimum pay-out length. In this way, an inflation of the belt webbing behind the upper deflection point is avoided. As a result, the gas quantity to be introduced into the belt interiors is minimized. In addition, any deformation of, damage to or loosening of paneling within the vehicle, behind which the belt webbing runs, is avoided, so that the risk of injury to the vehicle occupant(s) is minimized.
In a further embodiment, the tube is directly coupled to the gas generator, thereby forming a so-called gas lance. This advantageously results in a further improvement of the unfolding of the tube and consequently of the belt webbing, in particular in a shortening of the time leading to the unfolding.
The width of the belt webbing is preferably divided into several parts of approximately equal width, the belt webbing being folded once or several times parallel to its longitudinal dimension. In the region of the interior folded layers, the belt webbing is preferably woven thinner than in the region of the two outer folded layers. As a result, the belt webbing has an advantageously minimal thickness, a high flexibility and a low weight.
The folded layers are joined to one another by tear-open threads that break as the gas is applied to the belt webbing, followed by the unfolding of the belt webbing. In a collision of the vehicle, a surface area of the belt webbing is therefore increased as a result of its unfolding, thereby minimizing the load acting on the vehicle occupant.
The tear-open threads are inserted at the edges into the folded layers of the belt webbing in such a way that they form seams extending in the longitudinal direction of the belt webbing, these seams breaking when the gas acts on the belt interiors, i.e. when a resulting predetermined tensile load is exceeded. By the tear-open threads, the individual folded layers of the belt webbing are securely joined at the edges. The tear-open threads are inserted into the belt webbing in such a way that the latter maintains its flat shape in use. Furthermore, a defined unfolding of the belt webbing under the action of the gas is obtainable. In combination with the gas-tight design of the gas passage, an internal pressure within the gas passage can be maintained for a longer time, thereby facilitating an optimized and complete unfolding of the belt webbing.
In one variant, the width of the belt webbing is divided into three parts of approximately equal width, the belt webbing being folded twice parallel to its longitudinal dimension in such a way that it has a flattened Z-shape. After the unfolding of the belt webbing, a contact surface of the belt webbing on the vehicle occupant becomes almost three times as large as in the folded state, so that the force acting on the vehicle occupant is reduced in the region of the unfolding of the belt webbing.
Embodiments are explained in greater detail below with reference to drawings.